1. Field of the Invention
The protocol for certain agronomic studies such as those relating to the vegetative propagation of a plant species, involves isolation of roots or other plant tissue from soil core sample. Where the roots are very fine, this can be a difficult and tedious task. Due in part to the rather esoteric nature of this work, the technology for separating roots from soil has been slow to develop. As a result, advancements in this area of agronomy have also been less rapid than would have otherwise been expected.
2. Description of the Prior Art
Various devices have been constructed to extract the total root system of plants from field soil. One of the earliest root washers reported by H. A. Fribourg [Agron. J. 45: 334-335 (1953)] consisted of a stack of 14 wooden trays. Individual soil samples were placed into each tray and the stack was soaked in water containing a wetting agent. After soaking, the soil samples were placed on a slatted platform, and the loosened soil was washed from the roots with a spray of water. J. B. Fehrenbacher et al. [Agron. J. 47: 468-472 (1955)] described a design which consisted of eight pans with screened bottoms in which soil samples were placed. The pans were suspended in water and shaken. The soil settled through the screen, and the roots were skimmed off the water surface. In an apparatus reported by G. A. Cahoon et al. [Proc. Am. Soc. Hort. Sci. 78: 593-596 (1961)], angled jets of water were used to spin soil and roots on a cone within a container. The motion moved the roots and fine soil particles up the cone leaving the larger soil particles behind. The roots and fine soil particles dropped onto a classifying screen and were separated by washing.
In a more recent root washer designed by G. R. Brown et al. [J. Range Manage. 29: 506-507 (1976)], soil was placed into screen cannisters which were secured to a rotating agitator. As the agitator rotated through water, the soil was washed out of the cannisters and the roots retained inside. A washer reported by K. J. Ward et al. [Agron. J. 70: 675-677 (1978)] consisted of cloth bags filled with soil and suspended in water from laboratory wrist-action shakers. The shakers moved the bags in the water to wash out the fine soil particles. After removal from the bag, the roots were separated from the larger soil particles by decanting water which contained the floating roots. A root washing apparatus which relied upon application of pressurized water and air to soil samples submerged in water was reported by A. J. M. Smucker et al. [Agron. J. 74: 500-503 (1982)]. The combined action of the air and water loosened the roots from the soil. The loosened roots and fine soil particles floated to a screen which retained the roots but allowed the fine soil particles to be washed through. Fay et al. [Weed Sci. 26: 530-533 (1978)] disclosed an apparatus for extracting seeds from soil samples secured in nylon mesh bags. The bags were placed in a basket suspended from a crankshaft in a water tank. Vertical displacement of the basket in the tank provided the requisite agitation for removing soil particles from the bags.
By and large, the heretofore described devices were designed to wash relatively small volumes of soil, were highly labor intensive, and were not especially effective when applied to cohesive clay soils.